Cape Grim Baseline Air Pollution Station in Tasmania. Air samples collected here indicate that carbon emissions have more than doubled since the 1990s

Credit: David Whillas/CSIRO

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SYDNEY: The rate of increase in carbon dioxide emissions has more than doubled since the 1990s, according to a new Australian study, raising fears that the rising levels of carbon dioxide may be unstoppable.

"From 2000 to 2005, the growth rate of carbon dioxide emissions was more than 2.5 per cent per year, whereas in the 1990s it was less than one per cent per year," said study co-author Mike Raupach of Australia's national science agency, the CSIRO.

Carbon dioxide has been implicated as a major cause of global warming, and the new findings suggest that recent global efforts to reduce emissions have had little impact.

According to Raupach 7.9 billion tonnes of carbon were emitted into the atmosphere as carbon dioxide in 2005 and the rate of increase is accelerating.

Currently, China demonstrates the highest current growth rate in emissions, but its emissions per person are still below the global average and its accumulated contribution since the start of the industrial revolution around 1800 is only five per cent of the global total.

This compares to the U.S. and Europe, each of which have each contributed more than 25 per cent to accumulated global emissions.

The study examined a 30-year record of air samples collected at the Australian Bureau of Meteorology's observation station in Cape Grim, Tasmania, and was presented at the station's annual science meeting. Samples showed growth rates of just over one part per million in the early 1980s, but in recent years carbon dioxide has increased at almost twice this rate.

The amount of emitted carbon dioxide remaining in the atmosphere fluctuates from year to year due to natural factors such as El Niño. According to Raupach, on average nearly half of all emissions from fossil fuel use and land-use changes remain in the atmosphere, with the rest being absorbed by the land and oceans.

"A danger is that the land and oceans might take up less carbon dioxide in the future than they have in the past, which would increase the rate of climate change caused by emissions," he said.

"Recent emissions seem to be near the high end of the fossil fuel use scenarios used by the Intergovernmental Panel on Climate Change (IPCC). On our current path, it will be difficult to rein-in carbon emissions enough to stabilise the atmospheric carbon dioxide concentration at 450 ppm (the IPCC's goal for atmospheric carbon dioxide levels)."

According to CSIRO's Paul Fraser, another of the study's authors, "The trend over recent years suggests the growth rate is accelerating, signifying that fossil fuels are having an impact on greenhouse gas concentrations in a way we haven't seen in the past."

"The jump in emissions is remarkable … it seems there has been a tremendous shift in the past five years," said independent expert Paul Crutzen of the Max Plank Institute for Chemistry in Germany, a Nobel Prize winner for his work on holes in the ozone layer. "Unfortunately, once emissions go up, it's very hard to bring them back down."